The Deepwater Horizon oil spill, also referred to as the oil spill in the Gulf of Mexico oil or the Macondo blowout, is an oil spill which flowed unabated for three months in 2010. This blowout is considered one of the largest accidental marine oil spills in the history of the petroleum industry, and the spill stemmed from a sea-floor oil gush that resulted from the 20 Apr. 2010 explosion of the Deepwater Horizon rig which drilled on the Macondo Prospect. It is guessed that one of the primary reasons for the cause of the blowout is a defective cement job during completion of the well. Cement is used to seal between a first tubular and a borehole wall and between the first tubular and the next tubular. The cement is injected, and for some reason, the cement settles in the intended space, and during this process, unwanted pockets are formed in the cement or the cement disappears in an unexpected fracture in the formation. If the cement does not sufficiently fill the annular space, e.g. between the first tubular and the borehole wall, the oil may leak during production and gush through the cement or along the tubular, and an oil spill disaster may be the next step.
After the Macondo blowout, ensuring well integrity has been an increased focus of governments around the world, and thus also of the oil industry. To this effect, the downhole barrier systems incorporated in the well completion designs have been brought into focus to improve the well integrity.